Highly mobile small vehicles, sometimes called micro-robots, are better suited for certain missions than larger vehicles. For example, they can aid in search and rescue because their diminutive size enables them to fit into tight spaces, such as those found in rubble and in caves. As another example, a group of small robots provide robustness through redundancy for remote missions such as extraterrestrial exploration. Mobile small robots also are appropriate for insect inspired research because their scale is similar to that of the insect models.
A variety of such relatively small robots have been developed, but the majority of them have limited mobility. For example, some use small wheels and can move only on very smooth, flat surfaces. Others use relatively large wheels as compared to the size of the robots for improved mobility, but they still suffer from the limitations of wheels on complex terrain. Still others use tracks but at a relatively small scale it is difficult to implement a modern track suspension.
It is difficult for small robots to move through real-world terrain because of the relative size of the obstacles they must overcome. Therefore, there is a need for efficient locomotory appendages for relatively small robots. For example, for a given vehicle size, legs may provide the greatest mobility because they enable discontinuous contact with the substrate, which is advantageous for travel on uneven terrain. Insects are excellent examples of highly mobile legged vehicles.
Some robots have their basis in insect mobility. For example, RHex disclosed a simple and highly mobile insect-based hexapod robot. Int. J. Robotics Research, 20(7): 616-631. WHEGS™ (“wheel-like legs”) also disclosed insect-based robots in: Improved Mobility Through Abstracted Biological Principles, 2002 IEEE International Conference On Intelligent Robots and Systems, Lausanne, Switzerland. The disclosures of RHex and WHEGS™ robots are good examples of relatively large (e.g. on the order of about 50 cm long) hexapods that use abstracted cockroach locomotion principles to great effect. RHex uses six motors to independently rotate its legs. WHEGS™ robots, however, may use one propulsion motor and rely on preflexes to adapt their gaits to different terrain. Their driving appendages are sometimes called “WHEGS™” wheel-like legs, one example of which has three spokes and combines the speed and simplicity of wheels with the climbing mobility of legs. The “WHEGS™” equipped robots are several times faster, for example on the order of three (3) body lengths per second, than other legged robots of similar size and can climb obstacles that are relatively tall, e.g. on the order of about 1.5 leg lengths tall.